About Numbun

Known by many names around the world

This game family is most widely known in English as Bulls and Cows. In the classic rule set, a "bull" represents a correct digit in the correct position, while a "cow" means a correct digit in the wrong position. The game is traditionally described as a paper-and-pencil, code-breaking game of pure deduction [1].

The same core concept appears under various names around the world. In Chinese-speaking regions, it is commonly called 1A2B or 猜數字, where "A" marks a correct digit in the correct spot and "B" marks a correct digit in the wrong spot [2]. In Japan, similar versions are often known as Hit & Blow, a term that, along with "Cow & Bull," also appears in early technical documentation for the Multics game MOO [3].

In Korea, closely related number-guessing games are known as Number Baseball (숫자야구), using baseball terms like strike, ball, and out for clues. Depending on the region, you might also run into names like Picas y Fijas in Spanish, Taureaux et Vaches in French, Bullen und Kühe in German, Touros e Vacas in Portuguese, Быки и коровы in Russian, or Numerino and Numerello in Italian. These names don't need to share a single, definitive origin. Instead, they are simply local expressions of a universal logic concept that effortlessly travels across languages and cultures [4].

A short history

The exact origin of this game family is hard to pin down because it behaves more like a paper-and-pencil folk game than a single authored invention. Encyclopedic accounts describe Bulls and Cows as older than later commercial code-breaking board games, and Multics historical notes record Jerry Grochow's caution that MOO/Bulls and Cows was, as far as he knew, already a century-old game [1] [5].

The computer-era trail is better documented. Grochow's 1972 Software: Practice and Experience note says Cambridge's MOO was already popular when John Larmouth brought the idea to MIT in summer 1970, leading to a Multics version with a public score ladder and thousands of recorded games [6]. A 1971 Decuscope listing for MOO or BULLS and COWS shows the same four-digit bull/cow rules circulating through DECUS program-sharing culture for PDP and TSS/8 users [7]. Later, Donald E. Knuth's work on Master Mind showed that games in this code-breaking family were not only entertaining but also interesting algorithmic strategy problems; Knuth gave a constructive strategy that can identify any classic Master Mind code in at most five guesses [8].